1. Field of the Invention
The present invention relates to a motorcycle, and more particularly, to a rear suspension system for a motorcycle.
2. Background of the Invention
Motorcycle suspension systems come in a variety of different designs and configurations. Tsuchida, et al. (U.S. Pat. No. 4,724,920) discloses several prior art suspension systems that have various connection points between a frame and a rear fork. Tsuchida, et al. also proposes a rear suspension system that can raise the ground clearance of a motorcycle, that is, raise the minimum height of the motorcycle, but at the same time, reduce the center of gravity of the motorcycle.
Matsuura et al. (U.S. Pat. No. 5,592,999) discloses a height adjustable rear suspension system that uses a shock absorber link mechanism between a rear shock absorber and a swing arm. Ito (U.S. Pat. No. 6,290,017) discloses a rear suspension system that can be installed without affecting the shape and size of a fuel tank and a seat. The disadvantages of typical shock absorber-based rear suspension systems are noted by Thurm (U.S. Pat. No. 5,749,591), who discloses a rear suspension system that utilizes a leaf spring assembly. Thurm notes that the nature of a typical shock absorber-based system's suspension geometry permits very little shock absorber travel. This requires the shock absorbers to damp or absorb enormous amounts of force in very short working distances, sometimes several centimeters or less. Because of this, these systems tend to “bottom out” and usually provide a harsh ride.
Jurrens et al. (U.S. Pat. No. 6,003,628) and Crosby et al. (U.S. Pat. No. 6,357,546) disclose rear suspension systems that utilize air bags. The Jurrens air bag system does not provide enough shock absorber travel or range of motion. Another problem with the Jurrens system is the inherent complexity of the design, as noted by Crosby, Jr. Crosby's air bag system is also limited in its range of motion and can be difficult to repair or replace. The Crosby system compresses the air bag in an arc using a bag bracket. The bag bracket is a scissor-type linkage. This arrangement fails to keep the end pads of the bag in parallel relationship throughout the range of motion. Also, the Crosby system does not provide a system that can readily accept different types and sizes of air bags.